Russell Brand has opened up about one of his greatest romance failures - he couldn't persuade Forgetting Sarah Marshall co-star Mila Kunis to date him.

The funnyman admits he was smitten by the Black Swan beauty and tried everything to woo her, but Kunis refused to jeopardise her relationship with her boyfriend at the time to have a fling with the infamous Lothario.

Brand says, "She's so gorgeous. I was chatting her up, and got the conversation around to, 'Have you got a boyfriend?' and she went, 'Yeah'. So you know that feeling of, 'How long do I have to maintain an interest in this conversation now?' It's 12 seconds.

"She's talking about her boyfriend, Mac. Eventually, she said, 'My boyfriend's coming tomorrow'. She was excited - and when he came, it was not Mac, it was Macaulay Culkin!"

Kunis has since moved on from that romance and she is currently dating Ashton Kutcher.